1. Field of the Invention
The present invention relates generally to a liquid level gauge for use on a vehicle and, more particularly, to a liquid level gauge for indicating a liquid level in a tank on board a vehicle at response rates corresponding to the current speed of the vehicle on a real time basis.
2. Description of the Background Art
Heretofore, a number of proposals have been made regarding liquid level gauges for indicating the remaining quantity of a liquid such as fuel held in a tank mounted on board a vehicle. A conventional approach as disclosed Japanese Published Examined Patent Application No. Sho 60-1567 includes detecting a remaining fuel quantity in a fuel tank of a vehicle in terms of interelectrode capacitance, converting the detected value of interelectrode capacitance into an oscillation frequency of an RC oscillator, changing time intervals at which to measure a pulse count of the oscillation frequency between a stopped and a running state of the vehicle, and indicating the remaining fuel quantity on an indicator on the basis of an average of the measured pulse counts.
The following approach also disclosed in the above-noted Japanese Patent Publication includes using a float-equipped potentiometer type or a wire wound resistor type level gauge to detect the remaining fuel quantity in the fuel tank, inputting remaining quantity detection signals in analog form from the level gauge to an integrator for integration using different time constants between the stopped and the running state of the vehicle, and indicating the remaining fuel quantity on the indicator on the basis of the integrated value.
In a stopped state of the vehicle in accordance with the above-noted respective conventional approaches, the intervals at which to measure the pulse count are shortened and a shorter time constant is used in the integrator. In a running state of the vehicle in the above-noted respective conventional approaches, the measuring intervals are prolonged and a longer time interval is used in the integrator. These arrangements apparently allow the remaining fuel quantity to be indicated in a short time during a vehicle stopped state while permitting remaining fuel quantity indications through effective absorption of fuel level fluctuations during a vehicle running state.
However, conventional level gauges as above employ integrated values for indication purposes. Inevitably, averaging operations and concomitant time lags are introduced between actual and indicated remaining quantity. That is, the currently indicated remaining quantity at a given time merely represents an average of the quantities measured at points of time dozens of seconds and a few minutes prior to the given time. Accordingly, the value on the indicator is not the actual remaining quantity measured in real time.
In general, two-wheel vehicles (referred to as vehicle hereinafter) when parked have a side stand extended for support. Prior to being driven on the road, the side stand of the vehicle is folded off the ground so that the vehicle may run in an upright posture. Between the parked state (side stand extended) and the running state (side stand folded), the level in the fuel tank of the vehicle fluctuates and is often indicated as different values on the fuel indicator.
Motorcyclists sometimes begin driving the vehicle very short time after uprighting the vehicle from a parked position. In that short time period before activation, a precise fuel level measured during an upright posture of the vehicle must be indicated on the indicator.
The above-described conventional type of level gauge, however, involves determining and averaging a large number of actual liquid level measurements. The process necessarily requires extended time before the fluctuating liquid level is averaged and indicated on the indicator. In such cases, the motorcyclist begins riding the vehicle after checking the fuel level of the vehicle in a parked state with the side stand extended or after checking the fuel level while the vehicle is being uprighted from the parked state with the side stand folded. Accordingly, the motorcyclist must again check the fuel level while the vehicle is subsequently running in an upright posture.
A conventional approach to overcome the above-noted problem involves minimizing the averaging operation and the concomitant time lags between the actual and the indicated level by using time constants reduced to very small, almost negligible values. However, a problem with this conventional approach is that infinitesimal fluctuations of the liquid level can be picked up and presented as level indications that change too rapidly to be read meaningfully.
In addition, conventional level gauges are required to have three circuits: one for a larger time constant, another for a smaller time constant, and another for switching the two time constant circuits. These requirements complicate circuitry. An attempt to overcome this disadvantage includes replacing the three-circuit configuration with a conventional averaging circuit that performs averaging based on digital sampling. This requires switching between two averaging processes: one for totaling measurements taken in a relatively short time period of refueling and the other for totaling a large number of measurements taken over an extended period of time in the running state. As such, this conventional approach fails to provide simplified operating processes. In particular, the fact that the length to be averaged fluctuates, i.e. the population parameter for the division is varied, works against simplifying the operations involved. This is because averaging requires division.
It is therefore an object of the present invention to overcome the above and other deficiencies and disadvantages of conventional systems and to provide a liquid level gauge for use on a vehicle, the gauge indicating a liquid level of the vehicle in a start-up and a running state in accordance with requirements designated by a user of the vehicle, the level being indicated with little or no time lag.
The above and other objects may be fulfilled by providing a liquid level gauge for use on a vehicle, the gauge including a liquid tank mounted on board the vehicle; a liquid level detector for detecting a level of a liquid held in the liquid tank and for generating detection signals reflecting the detected level; an indicator driving controller for calculating, based on the detection signals, a value to be indicated to represent a liquid level; a liquid level indicator driven by the indicator driving controller; and a vehicle speed judgment unit for judging a speed of the vehicle. The indicator driving controller varies intervals at which to update data indicated on the liquid level indicator on the basis of judgments by the vehicle speed judgment unit. The indicator driving controller calculates the value to be indicated to represent the liquid level, based on values read from the liquid level detector within a time period shorter than the data updating intervals.
In a first preferred embodiment according to the invention, the intervals at which to update data indicated on the liquid level indicator are not greater than one second when the speed of the vehicle is less than five kilometers per hour, and are between five and sixty seconds when the speed of the vehicle is at least five kilometers per hour. In a second preferred embodiment according to the invention, at least the vehicle speed judging unit, the indicator driving controller and the liquid level indicator are housed in a case which accommodates a speedometer.
The invention when embodied in accordance with the above described features provides a liquid level gauge with little time lag in data indication on board the vehicle. That is, the inventive gauge allows the liquid level indicator to indicate, in real time or with a negligible time lag, liquid level data derived from the detection signals generated by the liquid level detector. The first preferred embodiment of the invention permits updating of liquid level data in less than one second if fuel level fluctuations are sufficiently small. This makes it possible to indicate precise level data in a suitably timed manner as required by the user of the vehicle. Furthermore, the second preferred embodiment enables provision of a liquid level gauge with a minimum number of components. This reduces assembling cost of the gauge.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.